power: Fix VSCR position on ucontext
Commit Message
Hi everyone,
I've working on a patch to fix the read of VSCR from ucontext in Power.
It was reading it from the wrong position on little endian machines
(ppc64le).
I'll appreciate a review on that patch
Regards
Comments
* Rogerio Alves:
> +#ifdef _ARCH_PWR8
Is it possible to perform run-time detection instead?
Thanks,
Florian
On Wed, 14 Nov 2018, Florian Weimer wrote:
>* Rogerio Alves:
>
>> +#ifdef _ARCH_PWR8
>
>Is it possible to perform run-time detection instead?
That's a fair point. Even though we have bots that test powerpc64
(big-endian) builds configured with `--with-cpu=power8', that's not the
default. Runtime detection could make this test work on default builds
(provided they are run on a POWER8 machine).
>+ /* Set SAT bit in VSCR register. */
>+ asm volatile ("vspltisb %0,0\n"
>+ "vspltisb %1,-1\n"
>+ "vpkudus %0,%0,%1\n"
Also, if you replace `vpkudus' (only available since Power ISA 2.07) with
`vpkuwus' (available since PowerISA 2.03) the test remains valid and it
could be tested on older machines.
From d52c4d0839ee77c0d8a2a0522ab4cbe0ce77587a Mon Sep 17 00:00:00 2001
From: Rogerio Alves <rcardoso@linux.ibm.com>
Date: Mon, 5 Nov 2018 10:18:38 -0600
Subject: [PATCH v2] powerpc: Fix VSCR position in ucontext.
This patch fix VSCR position on ucontext. VSCR was read in the wrong
position on ucontext structure because it was ignoring the machine
endianess.
2018-11-05 Rogerio A. Cardoso <rcardoso@linux.ibm.com>
* sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h
(struct _libc_vscr, vscr_t): Added ifdef to fix read of VSCR.
* sysdeps/powerpc/powerpc64/Makefile: Add tst-ucontext-ppc64-vscr.c
to test list.
* sysdeps/powerpc/powerpc64/tst-ucontext-ppc64-vscr.c: New test file.
---
Patch v2: fixed as per Gabriel and Segher review. Fix formating and changelog
Change the assembly inline to a better version. Changed ifdef to POWER8
sysdeps/powerpc/powerpc64/Makefile | 5 ++
.../powerpc/powerpc64/tst-ucontext-ppc64-vscr.c | 84 ++++++++++++++++++++++
sysdeps/unix/sysv/linux/powerpc/sys/ucontext.h | 5 ++
3 files changed, 94 insertions(+)
create mode 100644 sysdeps/powerpc/powerpc64/tst-ucontext-ppc64-vscr.c
@@ -59,3 +59,8 @@ $(objpfx)tst-setjmp-bug21895-static.out: $(objpfx)setjmp-bug21895.so
tst-setjmp-bug21895-static-ENV = \
LD_LIBRARY_PATH=$(objpfx):$(common-objpfx):$(common-objpfx)setjmp:$(common-objpfx)elf
endif
+
+ifeq ($(subdir),stdlib)
+CFLAGS-tst-ucontext-ppc64-vscr.c += -maltivec
+tests += tst-ucontext-ppc64-vscr
+endif
new file mode 100644
@@ -0,0 +1,84 @@
+/* Test if POWER vscr read by ucontext.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <support/check.h>
+
+#ifdef _ARCH_PWR8
+
+#include <ucontext.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <altivec.h>
+
+#define SAT 0x1
+
+static int
+do_test (void)
+{
+ uint32_t vscr[4] __attribute__ ((aligned (16)));
+
+ uint32_t* vscr_ptr = vscr;
+ uint32_t vscr_word;
+ ucontext_t ucp;
+ __vector __int128_t v0 = {0};
+ __vector __int128_t v1 = {0};
+
+ /* Set SAT bit in VSCR register. */
+ asm volatile ("vspltisb %0,0\n"
+ "vspltisb %1,-1\n"
+ "vpkudus %0,%0,%1\n"
+ "mfvscr %0\n"
+ "stvx %0,0,%2"
+ : "=v" (v0), "=v" (v1)
+ : "r" (vscr_ptr)
+ : "memory"
+ );
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ vscr_word = vscr[0];
+#else
+ vscr_word = vscr[3];
+#endif
+
+ if ((vscr_word & SAT) != SAT)
+ {
+ FAIL_EXIT1("FAIL: SAT bit is not set.\n");
+ }
+
+ if (getcontext (&ucp))
+ {
+ FAIL_EXIT1("FAIL: getcontext error\n");
+ }
+ if (ucp.uc_mcontext.v_regs->vscr.vscr_word != vscr_word)
+ {
+ FAIL_EXIT1("FAIL: ucontext vscr does not match with vscr\n");
+ }
+ return 0;
+}
+
+#else
+
+static int
+do_test (void)
+{
+ return FAIL_UNSUPPORTED("This test is unsupported on POWER < 8");
+}
+
+#endif /* _ARCH_PWR8_. */
+
+#include <support/test-driver.c>
@@ -98,8 +98,13 @@ typedef double fpregset_t[__NFPREG];
a whole quadword speedup save/restore. */
typedef struct _libc_vscr
{
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
unsigned int __pad[3];
unsigned int __ctx(vscr_word);
+#else
+ unsigned int __ctx(vscr_word);
+ unsigned int __pad[3];
+#endif
} vscr_t;
/* Container for Altivec/VMX registers and status.
--
2.7.4